1. Field of the Invention
This patent application relates to air brakes and more particularly to a tool for holding air brake components in position on a vehicle during maintenance procedures.
2. Background Information
Air brake systems such as those used on semi-trailer trucks typically include one or more air brake assemblies at each wheel. Certain tools are already known for assembling or servicing brake chambers. U.S. Pat. No. 4,776,079 describes a clamping tool for supporting a handbrake while slowly releasing it against the action of a compression spring. This tool serves to securely hold together the brake can and brake drum during repair procedures. The tool includes a pair of handles that pivot with respect to one another and a pair of clamping arms carried by the handle members. One of the clamping arms includes an adjustable support leg.
U.S. Pat. No. 6,009,608 describes a device for reassembling a brake system. The device includes a pair of jaws extending outwardly from vice grip type pliers. The upper jaw section has a notch cut out of one end for supporting an upper end of a brake chamber casing. The lower jaw section has an aperture for receiving a lower end of a casing shaft.
U.S. Pat. No. 7,942,083 describes a C-clamp locking device especially adapted to depress brake drum springs while brake shoes are replaced. This tool includes a pair of opposing jaws, with a first jaw having a ring disposed perpendicular to a blunt second jaw. Vice-grip type handle portions are used. This tool, while useful in repairing drum brakes, is not particularly helpful in servicing air brake chambers.
It is recognized that the safety precautions must be taken when working on or around brake chambers.
The purpose of a service brake is to convert the air pressure force generated when the driver steps on the brake pedal into a mechanical push rod action to engage brake shoes or pads.
A typical air brake assembly includes a housing (or chamber) with a diaphragm arranged to activate a push rod when air enters the chamber from an inlet. Air pressure is hydraulically controlled via a brake pedal accessible to the driver. A return spring helps to expel the air and return the push rod to its withdrawn position when air pressure is released. A vehicle's front brake chamber thus includes a housing assembly and diaphragm enclosed within a two-piece housing, the push rod return spring, and a band clamp which holds the two-pieces of the housing together.
A rear brake chamber is similar, but can be more complicated, because it often has two chambers, one for the service brake and another for an emergency or parking brake.
The emergency/parking brake utilizes a spring brake mechanism. The spring brake mechanism is not controlled by the same compressed air system as the service brakes. The spring brake is applied when air pressure leaves the brake chamber and releases when air pressure builds up in the chamber. Spring brake chambers work by means of a large coil spring that provides enough force to hold the brakes in the applied position instead of air. The spring brake section is, in effect, piggybacked onto a service brake section but these two sections function as two separate systems.